Journal of clinical monitoring and computing
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Improving the prediction of successful ventilator weaning and extubation is a goal that all Intensivists and perioperative physicians strive for. The successful wean and extubation of ventilated patients decreases hospital length of stay and associated costs, but more importantly it also reduces patient morbidity and mortality. ⋯ We also review the non-respiratory factors affecting weaning and the role of the bedside nurse and respiratory therapist. Resolution of the pulmonary compromise and an understanding of respiratory physiology, used in conjunction with monitored indices of weaning parameters in a consistent fashion will continue to improve our success rates of ventilator weaning and extubation.
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Traditionally, the study of CO2 and O2 kinetics in the body has been mostly confined to equilibrium conditions. However, the peri-anesthesia period and the critical care arena often involve conditions of non-steady state. ⋯ The lesser known area of non-steady state O2 kinetics is introduced, including the measurement of pulmonary O2 uptake per breath. Future directions include the study of the respiratory quotient per breath, where the anaerobic threshold during anesthesia is identified by increasing respiratory quotient.
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J Clin Monit Comput · Jan 2000
ReviewHRCT imaging of airway responsiveness: effects of anesthetics.
The noninvasive imaging method, high resolution computed tomography (HRCT), has been developed in animal models and applied to humans with obstructive lung disease for assessing regional and individual airway responsiveness. The ability to directly view airway responses during provocations such as tracheal intubation in an asthmatic could greatly enhance our understanding and treatment of airway hyperresponsiveness. HRCT uses increased kilovoltage peak (kVp) and milliamperage (mAs) settings, thin slices, high spacial frequency reconstruction algorithms, and small fields of view to resolve structures as small as 200 microm. ⋯ HRCT allows direct in vivo measurement of airway responsiveness to pharmacological and physiological stress that induces bronchoconstriction or bronchodilation. Using HRCT, we are able to measure airway dilation at baseline airway tone with inhalation anesthetics, differentiate the bronchodilating properties of inhalational agents in airways with tone, assess bronchodilating agents commonly used as premedications prior to anesthesia, and measure airway heterogeneity at baseline tone and their response to a variety of stimuli. This ability of HRCT to measure airway caliber and response heterogeneity in vivo noninvasively will dramatically improve our understanding of pulmonary physiology in general and the effects of anesthetics on the airways specifically.
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Pulmonary air embolism is a well-known consequence of surgery, trauma, diving, and aviation. This article reviews the physiological effects, means of detection and methods of prevention and treatment of pulmonary air embolism. The primary physiological effects are elevated pulmonary artery pressures, increased ventilation-perfusion inhomogeneity, and right ventricular failure. ⋯ Prevention measures include volume expansion, careful positioning, positive end-expiratory pressure, military anti-shock trousers, and jugular venous compression. Treatment of pulmonary air embolism includes flooding the surgical site with saline, controlling sites of air entry, repositioning the patient with the surgical site below the right atrium, aspiration of air from a central venous catheter, cessation of inhaled nitrous oxide, and resuscitation with oxygen, intravenous fluids, and inotropic agents. Some hypotheses on the effects of air in the pulmonary vasculature and investigational treatment options are discussed.
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J Clin Monit Comput · Jan 2000
ReviewNon-invasive imaging of regional lung function using x-ray computed tomography.
The use of imaging technologies has progressed beyond the depiction of anatomic abnormalities to providing non-invasive regional structure and functional information in intact subjects. These data are particularly valuable in studies of the lung, since lung disease is heterogeneous and significant loss of function may occur before it is detectable by traditional whole lung measurements such as oxygenation, compliance, or spirometry. ⋯ In addition, using the radiodense gas xenon (Xe) as a contrast agent, regional ventilation or gas transport may also be obtained. This communication will review recent advances in CT based techniques for the measurement of regional lung function.